The coolant used in association with machine tools is relatively costly, and an attempt is made to reuse same. However, during use, the coolant becomes highly contaminated with not only coarse contaminants such as machine chips and the like, but also fine contaminants which are difficult to remove. The coolant also becomes contaminated due to its contact with typical oils such as hydraulic fluids as used in association with machines, such oils being referred to as tramp oil, and becomes rancid.
At the present time, effective cleaning and reusing of coolant is limited by the ability to effectively remove the contaminants, particularly the fines, from the used coolant. While various techniques and apparatus have been utilized in an attempt to clean the coolant so as to permit reuse, nevertheless such techniques and apparatus have provided only limited results.
For example, one commonly used apparatus employs a separator wherein the contaminated coolant is deposited in a tank having a cleated drag conveyor movable along the bottom thereof, which conveyor collects thereon the coarse contaminants and removes them from the coolant. Such arrangement also often employs a skimmer for removing the tramp oil from the surface of the coolant. This known apparatus, however, is wholly unsuitable for removing the fines, and hence the coolant is only partially cleaned. Often the coolant is then supplied to a hydrocyclone, also such device does not effectively remove the fines.
Another known cleaning apparatus employs a paper bed filter positioned over a carrier chain, whereupon the contaminated coolant is deposited onto the filter and the contaminants create a filter cake thereon, whereupon the coolant filters downwardly by gravity into a collecting chamber. With such arrangement, the carrier chain and the paper filter are periodically advanced in an intermittent manner to sequentially move a clean filter under the inlet since the filter cake, after reaching a certain size, prevents any effective flow of coolant therethrough. While such arrangement is effective for removing fines, nevertheless such arrangement provides a very small flow rate therethrough, and the apparatus does not provide multiple filtering stages or steps so as to optimize both the rate and efficiency of the coolant cleaning operation.
Still another known technique or apparatus, and in fact the apparatus which has previously proven most effective in cleaning the coolant of fines so as to permit reclaiming and reuse of the coolant, employs a centrifuge as the critical element for effecting separation. In this known apparatus, the dirty coolant is supplied by a pump to a heater, and from there the dirty coolant is supplied to a centrifuge which, in a conventional manner, effects separation of the particles from the coolant, with the latter then being supplied to a coolant-receiving tank so as to be reused. Such apparatus, however, particularly due to the presence of the centrifuge, creates undesirable structural and functional complexities, particularly with respect to maintenance.
In view of the difficulty in satisfactorily cleaning the coolant to a sufficient degree to permit reclaiming and reusing, many manufacturing operations either do not reuse the coolant or are able to reuse only a small percentage thereof, and the remainder is disposed of. This is obviously undesirable since not only is the coolant expensive, but the disposal of the coolant creates a significant waste disposal problem. While extremely large manufacturers have provided systems which are able to clean the coolant with sufficient efficiency to permit its reuse, such manufacturers do so only by providing systems which normally provide multiple apparatus and hence often subject the coolant to numerous cleaning steps, with the coolant requiring significant handling and transporting between the various cleaning steps. Such systems themselves are bulky and space consuming, and are costly to install and operate. As such, such systems are wholly unsuitable for smaller manufacturers who produce smaller quantities of such contaminated coolant and who can not afford to invest in such large systems.
Accordingly, the present invention relates to an improved coolant reclamation unit which is believed to overcome many of the aforementioned disadvantages, and which is particularly desirable for use either by small manufacturers or for mounting on a truck or the like to enable it to be transported about so as to provide a reclaiming service for small manufacturers. This invention is particularly desirable for operation on the batch principle, that is, for cleaning a predetermined volume of contaminated coolant.
More specifically, the improved coolant reclamation unit of the present invention is a unitized self-contained unit which, in association with a single tank structure, performs an initial cleaning so as to effect removal of the coarse contaminants such as metal chips, with the coolant from the first cleaning tank then being supplied through a heater to a second cleaning tank having a filtering conveyor associated with the inlet thereof, which filtering conveyor has a paper filter associated therewith. The fluid from the first tank is supplied to the paper filter conveyor which is effective for removing fines, with the coolant flowing therethrough into the second tank. The coolant in the second tank is resupplied back to the paper filter unit at a location upstream from the supply from the first tank to more effectively remove the fines. The complete unit can be readily mounted on a truck and transported about so as to be usable at any selected job site.
Other objects and purposes of the present invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.